Benq FP71G+ frying noise

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • Dumah Brazorf
    Senior Member
    • Jun 2013
    • 179
    • Italy

    #1

    Benq FP71G+ frying noise

    Hi,
    repairing a benq. This works but make noise like frying and the backlight sometimes flashes to full bright. If the fry increase the screen may become black with power led remaining on and i have to power off and on again. The board is toasted on the point where seats the two LR3410 (expecially the upper one) that drive the only two inverter transformer. Caps checked, transformer's and others joints resoldered.
    I think i should change the LR3410 but i can't find them. Do you know an equivalent?
    Thanks.
    Attached Files
    Last edited by Dumah Brazorf; 09-12-2013, 11:31 AM.
  • viziks
    Member
    • Mar 2012
    • 33
    • India

    #2
    Re: Benq FP71G+ frying noise

    The explanation that pops up in my mind is that the CCFL tube must be defective cracked at one end and the frying sound is actually sparking.
    This would also account for the heating up on the board.
    You need to connect external CCFL (from Panel or spare) to confirm.

    Samir

    Comment

    • Dumah Brazorf
      Senior Member
      • Jun 2013
      • 179
      • Italy

      #3
      Re: Benq FP71G+ frying noise

      Hi, sorry for my late reply.
      I tore up the screen because there was some dust underneath so I can say that the hiss comes from the power board. After that I found that the leg of one 3kV cap was bend too close to one pin of one ccfl socket causing some little sparks. Well it was not enough so I finally found a reseller for LR3410.
      Today I changed both LR3410 (changed one first but found there was a huge difference in brightness between upper and bottom ccfls) and the hiss was dramaticaly reduced but not totally, and I still had that little blinking of the ccfls.
      Now it seems to work. What i've done is to clean the board removing thoroughly the soldering flux that remained after my previous works. I think that it was literally frying... d'oh!

      EDIT: Nope. It started again.
      Last edited by Dumah Brazorf; 09-23-2013, 09:18 AM.

      Comment

      • ben7
        Capaholic
        • Jan 2011
        • 4059
        • USA

        #4
        Re: Benq FP71G+ frying noise

        Check the wires going to the CCFL bulb(s) for arcing. Also check for shorted high voltage capacitors (those little blue ones).
        Muh-soggy-knee

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #5
          Re: Benq FP71G+ frying noise

          In this case, they will be brown/yellow disc caps by the lamp connectors.
          Bad wires:
          http://s807.photobucket.com/user/bud...tml?sort=3&o=9
          Never stop learning
          Basic LCD TV and Monitor troubleshooting guides.
          http://www.badcaps.net/forum/showthr...956#post305956

          Voltage Regulator (LDO) testing:
          http://www.badcaps.net/forum/showthr...999#post300999

          Inverter testing using old CFL:
          http://www.badcaps.net/forum/showthr...er+testing+cfl

          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
          http://s807.photobucket.com/user/budm/library/

          TV Factory reset codes listing:
          http://www.badcaps.net/forum/showthread.php?t=24809

          Comment

          • ben7
            Capaholic
            • Jan 2011
            • 4059
            • USA

            #6
            Re: Benq FP71G+ frying noise

            Originally posted by budm
            In this case, they will be brown/yellow disc caps by the lamp connectors.
            Bad wires:
            http://s807.photobucket.com/user/bud...tml?sort=3&o=9
            Whoops yeah that is what I meant ... I'm used to them usually being blue instead xD
            Muh-soggy-knee

            Comment

            • Dumah Brazorf
              Senior Member
              • Jun 2013
              • 179
              • Italy

              #7
              Re: Benq FP71G+ frying noise

              Thank you.
              Because the noise comes from the board I'll try new hv caps.

              Comment

              Related Topics

              Collapse

              • tony359
                Removing electrical noise introduced by fan
                by tony359
                Hi all,

                I am working on a sound processor, it tends to overheat so I fitted a fan inside. The fan is connected to the +15V of the PSU via a DC-DC converter based on the LM2596 to reduce the voltage to around 10.5V.

                Unfortunately the analogue circuitry is picking up the noise from the fan in two ways:
                1. The fan is close to the analogue section, the motor itself gets into the outputs so I'll have to move it somewhere else
                2. Even with the fan running outside of the case, there is still some noise which is clearly going back to the processor via power line....
                11-28-2023, 05:18 AM
              • MegaZAC
                Onkyo TX-SR805 noise in one channel
                by MegaZAC
                Surprisingly enough, this receiver doesn't have the DSP chip issue. The HDMI board does not get hot, and sound over HDMI works fine.

                Regardless of the input, the right channel has noise that is clearly noticeable even on average volume level. The only cases when there's no noise is when VCR input is selected (some tracks on the board are damaged, maybe that's why), or if HDMI input is selected but nothing plugged into it. In all other cases, even when no input is connected I still have the noise.

                There's some logic behind it. As soon as I select an input I get only left...
                04-23-2025, 10:09 PM
              • courtcircuit
                Philips HTS8000 home cinema noise problem
                by courtcircuit
                Hello

                I have since a long time a Philips HTS8010S/01 which has been old but was doing the job.

                Since a few days, it starts by making a weird "static" nois when switches on for a few seconds to a minute and then works like a charm.
                Noise loudly outputs from the 3 channels, even if no signal is sent by the controler.DVD to the subwoofer/amp unit.

                I was thinking of a soldering that was starting to be damaged and that was only doing the job after a few seconds of heating, most probbaly on the power board
                Removed each of tyhe boards
                ...
                02-08-2025, 08:22 AM
              • karatzdi
                Denon AVR 1908, High pitch noise on Surround back Left channel after long overhaul
                by karatzdi
                Hello,

                I know some might say... just buy another one. Sell it as parts..!

                So had this AMP for quite some time. Recently I saw light smoke coming out of the AMP. Had my fire extinguisher close by. Just kidding. Turned immediately all devices off from mains.
                Let things cool a bit, and opened up the amp device. I clearly saw on the main board which hosts the 5X amp (5.1), 3 10 ohms 1W resistors had their leads looking black, while the rest of the remaining 2 x 10 ohms were brownish as being installed from factory.

                Spent some time downloading the Service...
                06-11-2024, 08:38 AM
              • Biruslapio
                LG 50PB690 power supply terrible noise
                by Biruslapio
                I bought this TV with really bad oxidation on the power supply and bottom X boards, it was working but during pickup there was a lot of background noise so I don't know if it had this problem before.

                As soon as I could I opened the tv and started working on it, did not test it before since it had back bars on the screen and obvious signs of humidity. The X boards were replaced and the screen now works 100%, but the power supply...

                I washed the board and resoldered almost everything on the primary, the oxidation happened because of constant mains AC current flowing,...
                07-13-2022, 12:46 PM
              • Loading...
              • No more items.
              Working...